Some libraries use this pattern when they maintain a monorepo for a primary package. The main README.md needs to exist in the library that is published, so a neat trick with github is to symlink that at the root, so it is viewable on the monorepo landing page.
with my library on tangled: https://tangled.org/@tylur.dev/prototypey
on github: https://github.com/tylersayshi/prototypey
if you're open to contibution for this, I'd be happy to take a look!